Plowing and mulching are key to the potato harvest in China

When you think of China, do you think about potatoes? Maybe not, but in the Loess Plateau region of northwestern China, the potato is the main food crop.

Even though it is such an important crop in this region, potato yields are lower than what they could be. The region has a dry climate with uneven rainfall. Droughts are common, especially in the spring, when crops are just beginning to emerge. If soil moisture was more reliable, potato crops would do better.

Rong Li and colleagues at Ningxia University in Yinchuan, China, investigated whether different tillage and mulching practices could improve soil moisture – and crop yields – on the soil. Loess plateau. Researchers investigated three tillage options (conventional, direct sowing and subsoiling) associated with three mulching options (no mulch, straw mulch and plastic film).

Usually, fields in the Loess Plateau are plowed or plowed after harvest and left bare until spring planting. This is known as conventional tillage. Conservation tillage may mean not working the soil at all between crops (no tillage). Another conservation option is subsoiling: break the soil deeply with a long blade, without turning it over. Tillage helps the water to soak into the soil and improves soil storage.

"We did not know if tillage with varied mulching practices would improve drought resistance during the seedling stage of potatoes in these dryland growing areas."

The team studied the same field for two years – a relatively dry year followed by a wet year. For each combination of soil management options, they measured topsoil temperature, soil moisture content, seedling emergence rate, and marketable yield of potato tubers.

Plastic mulch warmed the soil more than other mulching options. Straw mulch had a refreshing effect compared to the lack of mulch. However, all three options produced soil temperatures in the range appropriate for rapid sprouting of the potato. It therefore appeared that topsoil temperature was not the key factor in early seedling growth.

Instead, the team concluded that drought was the main factor limiting agricultural production. Soil moisture during the sowing period is essential to the success of the crop. Techniques that maintained soil moisture improved both the rate of emergence and the establishment of seedlings. Both are essential for good tuber formation and marketable yield.

Other results include:

• Seedling emergence was lowest with conventional and mulch-free tillage compared to other treatments.
• The highest emergence rates were obtained when subsoiling was associated with plastic mulch.
• In the same tillage option, seedlings in mulch plots were much larger than those without mulch.
• Plots of straw mulch had the highest potato tuber yield, followed by plastic mulch.
• Soil conservation work (both tillage and subsoiling) with straw mulch resulted in higher potato yields and marketable tuber rates compared to other treatments.
• The highest yield of marketable tubers was found in the combination of subsoiling with straw mulch. This yield was 14.9% higher than conventional mulch free tillage.

Li and his team concluded that if the main goal was to increase the soil moisture, straw mulch should be chosen. Straw is also relatively inexpensive and environmentally friendly, while plastic mulch can cause pollution problems and is a less durable method.

"We recommend conservation tillage associated with straw mulch as a more favorable agricultural practice for the drought resistance of potato plants," said Li. "This combination offers great potential for greater agricultural production in our region and in similar semi-arid agricultural areas in the world. "

On the Loess Plateau, where the potato is king, these discoveries could be truly royal.

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Learn more about this research in Agronomic Journal. This work was supported by the National Natural Science Foundation of China.